Hydrothermally stable catalyst for improved lean NOx reduction
View Patent ↗Certain metal-exchanged SUZ-4 zeolites have been prepared that have catalytic activity for the reduction of NOx in the exhaust of a hydrocarbon or alcohol fueled engine operated under fuel lean conditions. Initially the SUZ-4 zeolite contains alkali metal cations such as Li + , Na + , K + and/or Cs + . These alkali metal cation-containing zeolites are partially exchanged with at least one of copper (II), silver (I), iron (III) or cobalt (II) ions. The resulting partially exchanged SUZ-4 zeolites display such activity and are stable under extreme hydrothermal aging conditions.
1. A NOx reduction catalyst for a hydrocarbon-fueled automotive engine operated at a fuel lean air-to-fuel ratio, said catalyst consisting essentially of a cation exchanged SUZ-4 zeolite, said zeolite having a Si/Al ratio of 5.1-6 and having potassium cations that have been partially exchanged with Cu (II).
2. The NOx reduction catalyst as recited in claim 1 in which the metal cation content consists essentially of 29 to 42% copper ions on the ion exchange capacity basis of said zeolite, and the balance said potassium cations.